Technical Field of the Invention
This invention relates generally to orthodontics and orthodontic appliances and, more particularly, to the characterization and treatment of malocclusions and to orthodontic brackets used in the treatment of orthodontitis, i.e., gingivitis caused by malpositioned teeth.
Description of the Related Art
Gingivitis is an inflammatory process affecting the soft tissues surrounding the teeth. Gingivitis describes inflammation of the gingivae, characterized by swelling, redness, influx of inflammatory cells, edema in the tissue, change of normal contours, and bleeding. Gingivitis is typically diagnosed when the gingiva appears red and puffy, loses its stippling, and bleeds spontaneously or on probing. Plaque-induced gingivitis is reversible by scaling and cleaning the teeth. However, if the bacterial plaque is not removed, the gingivitis progresses through the stages of chronic gingivitis and chronic periodontitis to chronic destructive periodontitis. Gingival pockets from tissue swelling and loss of attachment not involving bone are usually present. Gingivitis may be either acute or chronic, with emissions and exacerbations. General causes include hypovitaminosis, blood dyscrasias, allergic reactions, endocrine disturbances, such as diabetes mellitus, drugs such as diphenylhydantoin or the heavy metals, chronic debilitating disease or local factors such as dental calculus or plaque, food impaction, or faulty dental restorations and dental hygiene. The inhibition, prevention and treatment of gingivitis has varied little over the past two decades and consists primarily of establishing good oral hygiene and maintaining a periodontal environment that is easily kept clean by the patient. See, e.g., PCT Pub. Nos. WO 1996/009834 A1 and WO 1988/003021 A3; U.S. Pat. Nos. 3,577,520, 3,911,133 and 4,243,670; and European Pat. Pub. Nos. 0 345 039. Such topical and medicinal therapies are not only long and expensive, but never truly end. Moreover, such therapies are typically directed only at the resulting symptoms of gingivitis without addressing the underlying cause(s). Clearly, new modes of therapy are needed to substitute and augment current prophylaxis procedures.
Generally, treatment planning of orthodontic care is based primarily on the premise of improvements of function, dental and facial esthetics and general dental health. Recent clinical observation and experience has suggested that a common underlying cause of gingivitis is misaligned teeth or malocclusions. However, to date, a link between malocclusions and periodontal condition remains unclear and controversial. For example, the findings of one literature review on the impact of malocclusions and orthodontic treatment of periodontal health does not show a clear correlation (see Van Gastel, et al., Aust Orthod J 23(2): 121-129). Furthermore, a 2008 systematic review by Gray and McIntyre (see J. Orthod. 2008; 35: 262-9) shows a positive association of orthodontic care and periodontal health by quantifying the impact of orthodontic oral health promotion (OHP) which produced a reduction in plaque with an improvement in gingival health.
Nonetheless, at the outset it should be understood that a critical prerequisite for any effective orthodontic treatment is a proper understanding and classification of malocclusion. For without a proper understanding and classification of the problem (i.e., misaligned teeth), the effectiveness of any orthodontic treatment cannot be maximized. Currently there are several classifications of malocclusion, which include classic qualitative methods such as Dr. Edward Angle's classification and more contemporary quantitative methods and indices such as Peer assessment rating (PAR) and Index of orthodontic treatment need (IOTN). Considered by many to be the father of modern orthodontics, Dr. Angle was the first to classify malocclusion. First developed in the late 19th Century, Angle's classification system has remarkably endured the test of time and continues to be utilized as the main language of malocclusion among orthodontic specialists.
As shown in FIG. 1a, in accordance with the Angle's classification system, a proper or ideal occlusion has a molar relationship where the mesiobuccal cusp of the upper first molar 2 is aligned with the buccal groove of the mandibular first molar 4. The teeth should all fit on a line of occlusion which, in the upper arch, is a smooth curve through the central fossae of the posterior teeth and cingulum of the canines and incisors, and in the lower arch, is a smooth curve through the buccal cusps of the posterior teeth and incisal edges of the anterior teeth. Other factors for a proper occlusion include that all the teeth of the upper jaw are slightly over the lower teeth in the horizontal dimension (i.e., an overjet). A proper overjet 3 is from 2 to 3 mm. The teeth are formed in a nice uniform arch and there are no tooth rotations. Currently, dental professionals strive to obtain a proper occlusion when treating a malocclusion. Any variations from the proper occlusion results in malocclusion types, which are divided into three classes:                Class I Malocclusion: While the molar relationship of the occlusion is proper or normal, the other teeth have problems like spacing, crowding, over or under eruption, etc.        Class II Malocclusion—Overbite (FIG. 1b): A molar relationship where the mesiobuccal cusp of the upper first molar 2 is not aligned with the mesiobuccal groove of the lower first molar 4. Instead it is anterior to it. Any amount of overjet 3 more than 3 mm is not within normal limits.        Class III Malocclusion—Underbite (FIG. 1c): A molar relationship where the upper molars 2 are aligned posteriorly to the mesiobuccal groove and the lower front (anterior) incisor teeth 6 are farther forward than the upper incisors 7, resulting in an anterior crossbite. The mesiobuccal cusp of the maxillary first molar 2 lies posteriorly to the mesiobuccal groove of the mandibular first molar 4. It is usually seen when the lower front teeth 6 are more prominent than the upper front teeth 7.        
Yet, there continues to be an emerging body of literature that exposes the lack of evidence for this conventional classification of malocclusion. For example, one study showed poor diagnostic inter-provider reliability (see Gravely J F, Johnson D B. Angle's classification of malocclusion: an assessment of reliability. Br J Orthod 1974; 1:79-86) while another survey study among 34 chairpersons of Orthodontics Departments in the U.S. showed that fewer than 65% were in agreement on the meaning of a Class II sub-division. (see Siegel N A. A matter of class: interpreting sub-division in a malocclusion. Am J Orthod Dentofac Orthop 2002; 122: 582-586)
An editorial published in the American Journal of Orthodontics in 2009 stated that, although the concept of ideal occlusion has taken precedence as the ultimate goal in clinical orthodontics for some 110 years and serves as an adopted arbitrary method convention and clinical gold standard, it has no verifiable scientific validity, and that no one has yet demonstrated that ideal occlusion provides significant benefits in oral or general health, or that it significantly improves oral function. (see Ackerman, James and William Proffit: A not-so-tender trap, Am J Orthod Dentofacial Orthop 2009; 136:619-620)
A 2002 article also questioned the arbitrary nature of this classification that suggests a change in a stable, functional mandibular position in order to achieve a morphologic occlusion that conforms to an arbitrary ideal. (see Rinchuse, Daniel and Donald Rinchuse: Orthodontics justified as a profession, Am J Orthod Dentofacial Orthop 121:93-6, 2002) Indeed, the Angle Classification system is based upon a positioning of the teeth, which, it is estimated, teeth normally maintain for less than 20 minutes per day. Moreover, the arbitrary esthetic ideal of the Angle Classification system is thought to be based upon a euro-centric facial structure, which is structurally distinguishable from and unsuitable for the facial structure of other racial and ethnic groups.
Thus, the Angle Classification system inherently includes several drawbacks that hamper its ability to correctly define a proper occlusion or to diagnose malocclusions across a wide variety of patients from different and diverse racial and ethnic groups. Clearly, a new classification system is needed to more accurately define a proper occlusion and diagnose malocclusion. Moreover, a new classification system is needed to diagnose and treat patients based upon their individual genetic and morphologic appearance rather than an arbitrary ideal. Once the malocclusion has been correctly identified, treatment solutions can be implemented more effectively.